One of the purposes of this blog is to track the way in which companies are beginning to hijack the word "green" and use it to pump out all sorts of spurious marketing messages.

We saw a classic example today: a Glaswegian web hosting company NS Design said that it offered its customers a chance to go green - not by installing solar-powered web servers or by hosting them in a building made from recycled materials but by offering to plant a tree. NS Design isn't the first company to do this of course; Dell made such a pledge last year and Google has announced plans to go carbon neutral too.

Now there's nothing wrong with planting trees but there's plenty of wrong in making claims about carbon-offsetting for doing so. In fact, there's plenty of evidence that it's a misguided approach to reducing carbon emissions. As we've already reported, the Friends of the Earth decried the method and there's plenty of support for that notion.

However, there are plenty more organisations highly critical of the notion of planting trees as a means of off-setting carbon. The Carbon Neutral company, one of the most respected organisations in this field has stopped talking about planting trees because according to its website "it takes a tree 100 years to soak up the amount of CO2 a person could produce from driving in just 2 months. In terms of offsets, you can achieve the same CO2 reduction by changing your behaviour (eg buy green electricity) and, in terms of ‘offsets’, through technology shifts (like swapping kerosene burners in India with solar panels)".

Last year, a parliamentary committee was told that planting trees as an offset measure did more harm than good and money should be given direct to green charities - although as the advice was given by Jutta Kill of the er, green charity FERN, it might not have been the most unbiased advice ever.

But the problem isn't just with the effectiveness of the approach. The other problem faced by individuals looking to offset their carbon consumption is that the calculation is hideously complicated with different organisations using different methods to calculate their footprints - some of which can vary wildly.

In some ways, carbon offsetting has become the 21st century equvalent of buying indulgences - the mediaeval Catholic's way of salving his conscience by paying heavily to the church, just as the malefactor could be spared untold time in purgatory.

By all means, plant a tree if you want to, but let's have little less about carbon offsetting ... although something tells me that this won't be the last time we see this particular bit of marketing.